public static IHostBuilder AddScriptHost()

in src/WebJobs.Script/ScriptHostBuilderExtensions.cs [74:170]
69 lines of code
7 McCabe index (conditional complexity)

        public static IHostBuilder AddScriptHost(this IHostBuilder builder,
                                                 ScriptApplicationHostOptions applicationOptions,
                                                 Action<IWebJobsBuilder> configureWebJobs = null,
                                                 IMetricsLogger metricsLogger = null)
            => builder.AddScriptHost(applicationOptions, null, metricsLogger, configureWebJobs);

        public static IHostBuilder AddScriptHost(this IHostBuilder builder,
                                                 ScriptApplicationHostOptions applicationOptions,
                                                 ILoggerFactory loggerFactory,
                                                 IMetricsLogger metricsLogger,
                                                 Action<IWebJobsBuilder> configureWebJobs = null)
        {
            loggerFactory = loggerFactory ?? NullLoggerFactory.Instance;

            builder.SetAzureFunctionsConfigurationRoot();
            // Host configuration
            builder.ConfigureLogging((context, loggingBuilder) =>
            {
                loggingBuilder.AddDefaultWebJobsFilters();

                string loggingPath = ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "Logging");
                loggingBuilder.AddConfiguration(context.Configuration.GetSection(loggingPath));

                loggingBuilder.Services.AddSingleton<IFileWriterFactory, DefaultFileWriterFactory>();
                loggingBuilder.Services.AddSingleton<ILoggerProvider, HostFileLoggerProvider>();
                loggingBuilder.Services.AddSingleton<ILoggerProvider, FunctionFileLoggerProvider>();

                loggingBuilder.AddConsoleIfEnabled(context);

                loggingBuilder.ConfigureTelemetry(context);
            })
            .ConfigureAppConfiguration((context, configBuilder) =>
            {
                if (!context.Properties.ContainsKey(ScriptConstants.SkipHostJsonConfigurationKey))
                {
                    configBuilder.Add(new HostJsonFileConfigurationSource(applicationOptions, SystemEnvironment.Instance, loggerFactory, metricsLogger));
                }
                // Adding hosting config into job host configuration
                configBuilder.Add(new FunctionsHostingConfigSource(SystemEnvironment.Instance));

                var hostingEnvironmentConfigFilePath = SystemEnvironment.Instance.GetFunctionsHostingEnvironmentConfigFilePath();
                if (!string.IsNullOrEmpty(hostingEnvironmentConfigFilePath))
                {
                    configBuilder.AddJsonFile(hostingEnvironmentConfigFilePath, optional: true, reloadOnChange: false);
                }

                IConfiguration scriptHostConfiguration = applicationOptions.RootServiceProvider.GetService<IConfiguration>();
                if (scriptHostConfiguration != null)
                {
                    configBuilder.AddConfiguration(scriptHostConfiguration.GetSection(ScriptConstants.FunctionsHostingConfigSectionName));
                }
            });

            // WebJobs configuration
            builder.AddScriptHostCore(applicationOptions, configureWebJobs, loggerFactory);

            // Allow FunctionsStartup to add configuration after all other configuration is registered.
            builder.ConfigureAppConfiguration((context, configBuilder) =>
            {
                // Pre-build configuration here to load bundles and to store for later validation.
                var config = configBuilder.Build();
                var extensionBundleOptions = GetExtensionBundleOptions(config);
                FunctionsHostingConfigOptions configOption = new FunctionsHostingConfigOptions();
                var optionsSetup = new FunctionsHostingConfigOptionsSetup(config);
                optionsSetup.Configure(configOption);

                var extensionRequirementOptions = applicationOptions.RootServiceProvider.GetService<IOptions<ExtensionRequirementOptions>>();

                var bundleManager = new ExtensionBundleManager(extensionBundleOptions, SystemEnvironment.Instance, loggerFactory, configOption);
                var metadataServiceManager = applicationOptions.RootServiceProvider.GetService<IFunctionMetadataManager>();

                var locator = new ScriptStartupTypeLocator(applicationOptions.ScriptPath, loggerFactory.CreateLogger<ScriptStartupTypeLocator>(), bundleManager, metadataServiceManager, metricsLogger, extensionRequirementOptions);

                // The locator (and thus the bundle manager) need to be created now in order to configure app configuration.
                // Store them so they do not need to be re-created later when configuring services.
                context.Properties[BundleManagerKey] = bundleManager;
                context.Properties[StartupTypeLocatorKey] = locator;

                // If we're skipping host initialization, this key will not exist and this will also be skipped.
                if (context.Properties.TryGetValue(DelayedConfigurationActionKey, out object actionObject) &&
                    actionObject is Action<IWebJobsStartupTypeLocator> delayedConfigAction)
                {
                    context.Properties.Remove(DelayedConfigurationActionKey);

                    delayedConfigAction(locator);

                    // store the snapshot for validation later, but only if there
                    // are any registered external configuration startups.
                    if (locator.HasExternalConfigurationStartups())
                    {
                        context.Properties[ConfigurationSnapshotKey] = config;
                    }
                }
            });

            return builder;
        }